Abstract:

PURPOSE: In primates, vision is the most important sensation to collect information from the environment and guides the behavioral performance. In some occasions, the fast response is needed, such as express saccade, i.e. saccade with extremely short reaction time (latency). Express saccade has been considered to be generated through a short-cut visual-oculomotor pathway, which is usually not functioning. Previous studies suggest that the generation of express saccade requires advanced motor preparation. Motor preparation is a covert cognitive processing and might be contributed by many brain areas. Here we employed the ?xational saccade (micro-saccade) as a behavior probe to study this processing in express saccades.
METHOD: We compared the fixational saccade rate under express saccade condition and regular saccade condition. We also analyzed the fixational saccade rate under gap tasks with di?erent gap duration.
RESULTS: The results showed that the fixational saccade rate changed differently between express saccade and regular saccade: in short gap duration, the fixational saccade rate decreased much earlier in express saccade than in regular saccades; in medium and long gap durations, it decreased at similar time, but with a following rebound only in the regular saccade. Moreover, comparing between di?erent gap durations, the timing of ?xational saccade rate decrease was more related to the saccade initiation in express saccades, but more related to the physical disappearance of ?xation point in regular saccades. This suggests that the decrease of fixational saccade rate was closely related with saccade preparation in express saccade, but with visual transient in regular saccade.
CONCLUSIONS: Fixational saccade rate reflected that there was advanced motor preparation for express saccade.